Organizations such as on-line retailers, Internet service providers, search providers, financial institutions, universities, and other computing-intensive organizations often conduct computer operations from large scale computing facilities. Such computing facilities house and accommodate a large amount of server, network, and computer equipment to process, store, and exchange data as needed to carry out an organization's operations. Typically, a computer room of a computing facility includes many server racks. Each server rack, in turn, includes many servers and associated computer equipment.
Because the computer room of a computing facility may contain a large number of servers, a large amount of electrical power may be required to operate the facility. In addition, the electrical power is distributed to a large number of locations spread throughout the computer room (e.g., many racks spaced from one another, and many servers in each rack). Usually, a facility receives a power feed at a relatively high voltage. This power feed is stepped down to a lower voltage (e.g., 208 V). A network of cabling, bus bars, power connectors, and power distribution units, is used to deliver the power at the lower voltage to numerous specific components in the facility.
Some data centers include back-up components and systems to provide back-up power to servers in the event of a failure of components or systems in a primary power system. In some data centers, each primary power system may have its own back-up system that is fully redundant at all levels of the power system. For example, in a data center having multiple server rooms, each server room may have its own primary power system and back-up power system.
In some systems, an automatic transfer switch provides switching between alternate power systems. For example, an automatic transfer switch may switch power between a primary power system and a back-up power system. If the automatic transfer switch coupled to a rack system fails (for example, due to an overcurrent condition in the automatic transfer switch), the system may no longer be able to automatically switch to back-up power during a primary system failure.
In some cases, an automatic transfer switch that has properly functioned to switch to back-up power nevertheless fails to switch back to the primary power system once primary power has been restored. In this case, a power mismatch between primary power and secondary power downstream from the automatic transfer switch may cause a failure in the power system. In addition, having an automatic transfer switch stuck on back-up power even after primary power is restored may place strain on the back-up power system (keep the back-up system on a higher duty cycle that it is designed for).
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims. As used throughout this application, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words “include,” “including,” and “includes” mean including, but not limited to.